We provide biostatistics expertise for a number of NIEHS and NTP researchers, as well as researchers at universities and other government agencies who are conducting research related to the mission of the NIEHS. In these collaborations, we provide advice about study design, analyze data, interpret statistical results, and participate in writing papers for publication. Over the past year, we have been involved in the five research areas described below. As part of an NTP interagency agreement, we collaborated with researchers at NIOSH and the University of Cincinnati on a case-control study of the effects of genes and exposure to diisocyanates on the occurrence of occupational asthma. Based on our statistical analyses, we identified polymorphisms in several cytokine and antioxidant defense genes that are associated with occupational asthma. The polymorphism having the strongest association is within the superoxide dismutase (SOD2) gene. We collaborated with several NIEHS researchers who conduct research on mechanisms of DNA repair, mutation, and tumorigenesis. By testing for differences between genotype groups, calculating mutation probabilities and/or generating computer simulations of mutations, we found genes and sequences of genomic events involved in mutations and DNA repair. We collaborated with NIEHS and extramural researchers who are mining survey data to discover associations between environmental exposures and disease. In one study, we examined the association between tubal ligation and breast cancer risk and found no increased risk. In other studies, we found that coronary stents coated with a drug were more effective in preventing thrombosis than bare metal stents, and that thrombosis is more likely several years after a stent is placed in a coronary artery compared to simply expanding the diameter of the artery through angioplasty. We also contributed to a study of associations between reproductive and hormonal status and prevalence of antinuclear antibodies in U.S. women. We contributed to studies that characterized the histopathological features of uterine fibroids, the adhesion of cells that occurs in cancer, and the research-related compensation policies of U.S. research institutions. Finally, we examined the stability of bisphenol A concentrations assayed in urine specimens across a variety of experimental conditions. The results of these analyses were used to determine how specimens should be handled when this assay is used in epidemiological studies.